Absorbent articles, such as disposable infant diapers, feminine care products, incontinence garments and the like, have included high absorbency superabsorbent polymers to increase the absorbent capacity of the article and to reduce the bulkiness of the article. For example, see U.S. Pat. No. 3,669,103 to Harper, U.S. Pat. No. 3,670,731 to Harmon, and U.S. Pat. No. 4,087,506 to Cook et al. Particular absorbent article designs have concentrated superabsorbent polymers in selected regions of the absorbent pad. For example, see U.S. Pat. No. 4,381,782 to Mazurak et al., U.S. Pat. No. 4,410,324 to Sabee and U.S. Pat. No. 4,461,621 to Karami et al. In some of these conventional arrangements, the high absorbency material, such as superabsorbent polymer, have been substantially uniformly mixed with absorbent fibers located within selected layers, or strips. In other arrangements, the high absorbency material has been substantially isolated in layers, zones or pockets within the absorbent pad with the high absorbency material substantially unmixed with the absorbent fibers.
Various devices and processes have been employed to manufacture absorbent article designs. Air forming techniques for forming webs of hydrophilic fibers, such as woodpulp fibers, are well known in the art. In addition, it is well known that superabsorbent polymers may be mixed with the hydrophilic fibers during an airlaying process to form an absorbent web. For example, see the Sanyo Technical Bulletin entitled "SAP SHEET", dated October 1982.
Particular absorbent article designs have particles of superabsorbent polymer localized in selected regions. For example, U.S. Pat. No. 3,888,257 issued June 10, 1975 to R. Cook et al. describes a disposable absorbent article in which a rectilinear, central zone of a matrix of fiberized woodpulp incorporates a 3-dimensional dispersion of hydro-colloid polymer particles. U.S. Pat. No. 4,381,782 issued May 3, 1983 to P. Mazurak et al. describes an absorbent article wherein hydrogel material is incorporated by placement near a front edge of an absorbent batt in a diaper article. Other designs have incorporated superabsorbent materials within selected layers, longitudinal strips, lateral strips and other types of isolated zones or regions.
Various methods and apparatus have been employed to manufacture absorbent articles. For example, U.K. Patent Application, GB 2,150,033 A published June 26, 1985, describes a suction drum apparatus for making an absorbent pad wherein an integrated shell of flocculent material surrounds an internal absorbent layer. U.S. Pat. No. 4,087,508 issued May 2, 1978 to R. Cook et al. describes a method which includes applying hydrocolloid polymer particles onto the surface of a central zone of a moving web, and distributing the applied particles into the body of the moving web by air-pressure means. International Patent Application No. WO 88/04165 published 16 June 1988 described a method and apparatus for forming a nonwoven pad consisting of fibrous material in which highly moisture-absorbent particles are intermixed with the fibrous material throughout a predetermined portion of the thickness of the nonwoven pad. A spray gun or an extension thereof is positioned within the chamber relative to the fibrous material atop a conveyor and is operated to discharge moisture-absorbent material at a predetermined velocity, such that the moisture-absorbent material is intermixed with the fibrous material throughout a central layer of the thickness of the nonwoven pad while forming boundary layers on either side of the center layer which are substantially free of moisture-absorbent material. The spray gun preferably operates intermittently to form spaced, sharply defined areas along the length and width of the nonwoven pad wherein each area has moisture absorbent material interspersed throughout a portion of the thickness thereof.
Conventional methods and apparatus, such as those described above, have not been sufficiently satisfactory. For example, the devices may be overly complex and expensive and may not provide desired patterns of deposition for particulate materials, such as superabsorbent granules. The rate of delivery of the superabsorbent particles may not be adequately controlled, and the systems may be excessively sensitive to changing bulk densities in the particulate material.